高比能锂离子电池层状富锂正极材料改性策略研究进展

层状富锂材料具有超过250 mAh∙g⁻¹的高可逆比容量,被认为是下一代高比能锂离子电池最具商业化前景的正极材料之一。然而,层状富锂材料在实际应用之前仍需解决诸多挑战,如高电压氧释放、层状到岩盐相的结构变化、过渡金属离子迁移等结构劣化,并由此带来了较低的初始库伦效率、电压/容量的衰减以及循环寿命的不足。针对以上问题,进行层状富锂材料改性无疑是一种行之有效的方法。本综述全面介绍了层状富锂材料的结构、组分以及电化学性能,在此基础上对材料改性策略进行了系统阐述,详细介绍了体相掺杂、表面包覆、缺陷设计、离子交换和微结构调控等一系列改性策略的现状以及发展趋势,最终提出了高容量和长循环层状富锂材料和高比能锂离子电池的设计思路。     

Chemo‐ and Regioselective Dihydroxylation of Benzene to Hydroquinone Enabled by Engineered Cytochrome P450 Monooxygenase

Hydroquinone (HQ) is produced commercially from benzene by multi‐step Hock‐type processes with equivalent amounts of acetone as side‐product. We describe an efficient biocatalytic alternative using the cytochrome P450‐BM3 monooxygenase. Since the wildtype enzyme does not accept benzene, a semi‐rational protein engineering strategy was developed. Highly active mutants were obtained which transform benzene in a one‐pot sequence first into phenol and then regioselectively into HQ without any overoxidation. A computational study shows that the chemoselective oxidation of phenol by the P450‐BM3 variant A82F/A328F leads to the regioselective formation of an epoxide intermediate at the C3=C4 double bond, which departs from the binding pocket and then undergoes fragmentation in aqueous medium with exclusive formation of HQ. As a practical application, an E. coli designer cell system was constructed, which enables the cascade transformation of benzene into the natural product arbutin, which has anti‐inflammatory and anti‐bacterial activities.     

Carbon Vacancies in a Melon Polymeric Matrix Promote Photocatalytic Carbon Dioxide Conversion

Photosynthetic conversion of CO₂ into fuel and chemicals is a promising but challenging technology. The bottleneck of this reaction lies in the activation of CO₂, owing to the chemical inertness of linear CO₂. Herein, we present a defect‐engineering methodology to construct CO₂ activation sites by implanting carbon vacancies (CVs) in the melon polymer (MP) matrix. Positron annihilation spectroscopy confirmed the location and density of the CVs in the MP skeleton. In situ diffuse reflectance infrared Fourier transform spectroscopy and a DFT study revealed that the CVs can function as active sites for CO₂ activation while stabilizing COOH* intermediates, thereby boosting the reaction kinetics. As a result, the modified MP‐TAP‐CVs displayed a 45‐fold improvement in CO₂‐to‐CO activity over the pristine MP. The apparent quantum efficiency of the MP‐TAP‐CVs was 4.8 % at 420 nm. This study sheds new light on the design of high‐efficiency polymer semiconductors for CO₂ conversion.     

Observations of Runaway Electron Generation during Disruptions on HL-2A Tokamak

The major disruption can not only lead to the great heat loads and produce the large electromagnetic force on the first wall and divertor plates, but also can generate the runaway electrons. The runaway electrongeneration is a dangerous event for tokamak operation.     

SO和LO声子对GaAs-Ga1-xAlxAs量子阱中激子束缚能的影响

本文考虑了电—声子耦合作用,应用么正变换方法计算了GaAs-Ga1-xAlxAs量子阱中的激子束缚能;得到了激子束缚能随阱宽变化的曲线。当考虑激子声子相互作用后,激子相对于电子极化子和空穴极化子的第一子带底的束缚能小于相应的裸激子的束缚能量。     

N-vinyl pyrrolidone promoted aqueous-phase dehydrogenation of formic acid over PVP-stabilized Ru nanoclusters

In this work, we fabricated the poly(N-vinyl-2-pyrrolidone)(PVP)-stabilized ruthenium(0) nanoclusters by reduction of RuCl_3 using different reducing agents, and studied their catalytic activity in hydrogen generation from the decomposition of formic acid.It was demonstrated that N-vinyl-2-pyrrolidone(NVP), which is a monomer of PVP, could promote the reaction by coordination with Ru nanoparticles. The Ru nanoparticles catalyst reduced by sodium borohydride(NaBH_4) exhibited highest catalytic activity for the decomposition of formic acid into H_2 and CO_2. The turnover of numenber(TOF) value could reach 26113 h~(–1) at 80 °C. We believe that the effective catalysts have potential of application in hydrogen storage by formic acid.